Question

(X+2分之3X-X-2分之X)+X的平方-4分之2X,其中X=4-根号5

Answer 1

(X+2)分之3X-(X-2)分之X+(X的平方-4)分之2X

=3x(x-2)/[(x-2)(x+2)]-x(x+2)/[(x-2)(x+2)]+2x/[(x-2)(x+2)]

=[3x(x-2)-x(x+2)+2x]/[(x-2)(x+2)]

=2x(x-3)/[(x-2)(x+2)]

=2(4-√5)(4-√5-3)/[(4-√5-2)(4-√5+2)]

=2(9-5√5)/(17-8√5)

=(94-26√5)/31